Abstract
Kinetic models of solid-state reactions are often based on a formal description of geometrically well defined bodies treated under strictly isothermal conditions; for real processes these assumptions are evidently incorrect. The kinetic parameters are distorted by the difference of the real process from the idealized kinetic model. In this respect, it can be useful to find an empirical function containing the smallest possible number of constants, so that there is some flexibility enough to describe real process as closely as possible. In such a case the models of heterogeneous kinetics can be assumed as a distorted case of the simpler homogeneous kinetics and then mathematically treated by multiplying an “accommodation” function. The empirical function also accommodates the deviation of the non-isothermal process from the process under the isothermal condition. The mutual dependence of the Arrhenius parameters observed empirically is recognized as a simple mathematical consequence of the exponential form of the rate constant in the Arrhenius equation, resulting from both the poorly controlled measuring condition in the thermal analysis and the false kinetic treatment. The isoconversion method allows to check the invariance of the activation energy during the course of reaction, which is the fundamental assumption in the derivation of the kinetic equation. Once the characteristic activation energy is determined, it is possible to find the kinetic model function which best describes the measured set of TA data using the two special functional relationships in the kinetic equation.
